Hydrogen bonding

Question

Explain how a hydrogen bonding is formed and state whether it is an intermolecular or a intramolecular attraction

Answer 1

A hydrogen bond is formed between H and O or N. The H is usually on one molecule and the O or N is usually on another. The H and the O or N can be on the same molecule if a ring can be made by the H bonding to the O or N. The H is bonded polar covalently to a negatively charged atom which gives makes it have a partial positive charge. The same H atom is hydrogen bonded to a nearby O or N atom.

An example of two separate molecules would be a pure alcohol or solution of alcohol and water. The OH of the alcohol or water lines up with the OH of another alcohol or water so that the H of one molecule is next to the O or another and hydrogen bonds to it. This is intermolecular bonding - between two molecules.

In an example of the same molecule there is a molecular part between an O of a aldehyde part and an OH of a hydroxide part. The aldehyde O and the H of the hydroxide hydrogen bond together making a ring.

A meta substituted phenyl ring could have aldehyde and acidic constituents. The hydrogen bond containing ring would be made by the hydrogen bond of the aldehyde and the acid. This is intramolecular bonding - within the same molecule.